What did Euler wrongly assume when he first derived pi^2/6 from the infinite sum of 1/n^2? Doctor Jordan reveals two missteps initially committed by the famous mathematician on this now-classic result.

Why is it that when two complex numbers are graphed, then the sum of
those two complex numbers is graphed (all of this on the same graph),
and then lines are drawn to connect the parts of each graph farthest
from the origin, a parallelogram is formed?